Valve Timing Control Apparatus

ABSTRACT

A valve timing control apparatus includes a driving rotary member to receive a rotational force from a crankshaft of an engine, and a vane rotor connected with a camshaft and arranged to rotate relative to the driving rotary member, with at least one vane defining a retard pressure chamber and an advance pressure chamber in the inside of the driving rotary member. A lock member is received slidably in the vane of the vane rotor and arranged to engage with a lock hole when the vane is rotated to a predetermined angular position. The lock member includes forward and rearward end portions arranged to receive equal fluid pressures. The lock member further includes a pressure receiving portion to which an operating fluid pressure is selectively applied to force the lock member away from the lock hole.

BACKGROUND OF THE INVENTION

The present invention relates to valve timing control apparatus for controlling the opening timing and/or closing timing of an engine valve such as an intake valve and an exhaust valve of an internal combustion engine.

A vane type valve timing control system of a known type includes a lock mechanism including a lock hole formed in a housing of a sprocket on a driving side, and a lock pin which is slidably received in a vane rotor joined to a camshaft and which is arranged to engage with the lock hole to lock the vane rotor unrotational at an intermediate phase position between a most advance position and a most retard position.

The valve timing control system of this type maintains a lock state of the vane rotor until the oil pressure supplied from an oil pump to a retard pressure chamber or an advance pressure chamber is increased at the time of engine start, and maintains an unlock state by utilizing the oil pressure of the oil pump after the oil pressure is increased.

Therefore, a valve timing control system as disclosed in Patent Document (JP2003-222010 A) is arranged to achieve a desired control timing by holding and canceling the lock state by using a hydraulic pressure of a hydraulic circuit different from a hydraulic circuit for the retard pressure and advance pressure.

SUMMARY OF THE INVENTION

However, the above-mentioned valve timing control system uses a lock having an annular shoulder surface formed between a large diameter portion and small diameter portion and selectively applies the fluid pressure to the annular shoulder surface. Accordingly, to ensure smooth axial movement of the lock pin, the lock pin is so arranged that both axial ends of the lock pin are always open to the atmosphere.

Therefore, to prevent leakage of the oil pressure in the retard or advance chambers, the system requires a longer side seal having a longer circumferential length for sealing the clearance between one axial end of the lock pin and the inside surface of the housing, and hence requires an increase of the circumferential width of the vane, so that it becomes difficult to increase the operating rotational angle of the vane.

Therefore, it is an object of the present invention to provide a valve timing control apparatus for an internal combustion engine, suitable for ensure a large operation angle of a vane rotor despite a lock pin moved axially by using an operating fluid pressure of a separate system.

According to one aspect of the present invention, a valve timing control apparatus comprises: a driving rotary member; a vane rotor; a lock member received in the vane and arranged to slide forwards and rearwards in an axial direction; and a lock hole to receive a forward end of the lock member; wherein the lock member includes a forward end portion to receive a first fluid pressure which is one of a fluid pressure in the retard pressure chamber and a fluid pressure in the advance pressure chamber in a pressure receiving area, and a rearward end portion to receive the first fluid pressure in a pressure receiving area, the pressure receiving area of the forward end portion receiving the first fluid pressure being equal to the pressure receiving area of the rearward end portion receiving the first pressure; and wherein the lock member further includes a pressure receiving portion including a first surface to which an operating fluid pressure is selectively applied, and a second surface which is opened through an air passage formed in the vane rotor, to atmosphere.

According to another aspect of the invention a valve timing control apparatus comprises: a driving rotary member; a vane rotor; a lock member received in the vane and arranged to slide axially; a lock receiving portion to receive a forward end portion of the lock member when the vane is at a predetermined intermediate position between a most retard position and a most advance position; and a biasing member to urge the lock member toward the lock hole; wherein the lock member includes a forward portion to receive a first fluid pressure which is one of a fluid pressure in the retard pressure chamber and a fluid pressure in the advance pressure chamber in a pressure receiving area, and a rearward portion to receive the first fluid pressure, a pressure receiving area of the forward portion receiving the first fluid pressure being equal to a pressure receiving area of the rearward portion receiving the first pressure; and wherein the valve timing control apparatus further comprises a canceling section to release the lock member from the lock receiving portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a valve timing control apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view taken across a line II-II shown in FIG. 1, showing a vane rotor or vane member at an intermediate phase angular position.

FIG. 3 is a sectional view taken across the line II-II shown in FIG. 1, showing the vane rotor at a most retard phase position.

FIG. 4 is a sectional view taken across the line II-II shown in FIG. 1, showing the vane rotor at a most advance phase position.

FIG. 5 is a sectional view, taken across a line V(i)-V(i) and a line V(ii)-V(ii) shown in FIG. 2, showing first and second lock pins in a first operating state.

FIG. 6 is a sectional view, taken across the line V(i)-V(i) and the line V(ii)-V(ii) shown in FIG. 2, showing the first and second lock pins in a second operating state.

FIG. 7 is a sectional view, taken across the line V(i)-V(i) and the line V(ii)-V(ii) shown in FIG. 2, showing the first and second lock pins in a third operating state.

FIG. 8 is a sectional view, taken across the line V(i)-V(i) and the line V(ii)-V(ii) shown in FIG. 2, showing the first and second lock pins in a fourth operating state.

FIG. 9 is a sectional view, taken across the line V(i)-V(i) and the line V(ii)-V(ii) shown in FIG. 2, showing the first and second lock pins in a fifth operating state.

FIG. 10 is a sectional view, taken across the line V(i)-V(i) and the line V(ii)-V(ii) shown in FIG. 2, showing the first and second lock pins in a sixth operating state.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1˜10 show a valve timing control apparatus according to an embodiment of the present invention. In this embodiment, the valve timing control apparatus is applied to the intake valve's side of an internal combustion engine for a vehicle such as a hybrid vehicle or a vehicle provided with an idle stop system.

As shown in FIGS. 1˜4, the valve timing control apparatus according to the embodiment includes a sprocket 1, a camshaft 2 on the intake side, a phase varying mechanism 3 and a first hydraulic circuit 4. The sprocket 1 is connected by a timing chain with a crankshaft of the engine and adapted to be driven by the engine. Sprocket 1 serves as a driving rotary member driven by the engine. The camshaft 2 extends in the front and rear direction of the engine. Camshaft 2 is rotatable relative to the sprocket 1. The phase varying mechanism 3 is disposed between sprocket 1 and camshaft 2, and arranged to vary the relative rotational phase of the sprocket 1 and camshaft 2. The first hydraulic circuit 4 is arranged to actuate the phase varying mechanism 3.

Sprocket 1 is a thick plate shaped like a circular disk. Sprocket 1 includes a toothed portion 5 formed in an outer circumferential portion and arranged to engage with the timing chain. Sprocket 1 is arranged to close a rear opening of a housing (7), and thereby to serve as a rear cover. Sprocket 1 includes a support hole 6 opened through a central portion of sprocket 1, and arranged to receive a vane rotor (9) rotatably. Vane rotor or vane member (9) is fixed to camshaft 2.

Camshaft 2 is rotatably supported through cam bearings on a cylinder head (not shown). Camshaft 2 includes a plurality of cams which are integrally formed at positions arranged in the axial direction, and which are designed to open a plurality of engine valves (intake valves in this embodiment). Camshaft 2 extends from a second end to a first end (left end as viewed in FIG. 1) which is formed with a female threaded (or internally threaded) hole 2 a extending along the center line of camshaft 2.

As shown in FIGS. 1 and 2, the phase varying mechanism 3 includes a housing 7 joined axially to sprocket 1 so as to form a single unit, and a vane rotor or vane member 9 serving as a driven rotary member. The vane rotor or member 9 is fixed to the first (left) end of camshaft 2 through a cam bolt 8 screwed into the female threaded hole 2 a of camshaft 2, and received rotatably in housing 7. Housing 7 includes partition walls 10 projecting radially inwards from a circumferential wall, and serving as shoes. The partition walls 10 and vane member 9 define retard pressure chambers 11 and advance pressure chamber 12. In this example, there are three of the partition walls 10, three of the retard chambers 11 and three of the advance chambers 12.

Housing 7 of this example includes a main housing member 7 a of sintered metallic material having a hollow cylindrical shape, a front cover 13 closing a front opening of the main housing member 7 a, and the rear cover formed by the sprocket 1 and arranged to close the rear opening of main housing member 7 a. The main housing member 7 a, front cover 13 and sprocket 1 are joined together by bolts 14 (three bolts) passing, respectively, through bolt holes 10 a opened, respectively, in the partition walls 10. Front cover 13 includes a central through hole 13 a.

Vane rotor or vane member 9 is a single integral member of a metallic material including a central rotor 15 fixed to the first (left) end of camshaft 2 by cam bolt 8, and a plurality (three) of vanes 16 a, 16 b and 16 c projecting radially outwards from the outside circumferential surface of central rotor 15, respectively, at positions arranged around the center axis at substantially regular angular intervals (in this example, 120 degrees).

Central rotor 15 extends from a front (first) end 15 b to a rear (second) end 15 c in the front and rear direction in the form similar to a hollow cylinder. The front end 15 b is formed integrally with a tubular seal guide portion 15 a which is located approximately at the center of the front end 15 b and which has a thin wall tubular shape of a smaller diameter so as to form a step. The rear end 15 c includes an extension extending toward camshaft 2. Central rotor 15 includes an inside cylindrical engagement hole or bore 15 d extending from the front end toward the rear end inside the central rotor 15.

Vanes 16 a˜16 c of vane rotor 9 and partition walls 10 of housing 7 are arranged alternately around the center axis so that each vane is disposed circumferentially between adjacent two of the partition walls 10. Vanes 16 a˜16 c are unequal in circumferential width in the circumferential direction. The vane 16 a having a greatest width and the vane 16 b having a medium width are shaped like a fan or a circular sector. The vane 16 c having a smallest width is shaped like a projecting thick plate. The radial outward end of each of vanes 16 a˜16 c is provided with a seal member 17 a for sealing the boundary portion between the vane and the inside circumferential surface of main housing member 7 a. The radial inward end of each of partition walls 10 of main housing member 7 a is provided with a seal member 17 b for sealing the boundary portion between the outside circumferential surface of central rotor 15 and the radial inward end of the partition wall 10. As best shown in FIG. 2, the widest vane 16 a includes a first side surface 16 d facing in the counterclockwise direction, and a second side surface 16 e facing in the clockwise direction.

When vane member 9 is rotated relatively to the retard side (in the counterclockwise direction), as shown in FIG. 3, the above-mentioned first (retard) side surface 16 d (shown in FIG. 2) of the widest vane 16 a on the retard side abuts against a projecting surface 10 b formed in a confronting side surface of the adjacent partition wall 10 on the retard side (or counterclockwise side), and this abutment determines the rotational angular relative position of vane member 9 of the greatest retard angle. When vane member 9 is rotated relatively to the advance side (in the clockwise direction), as shown in FIG. 4, the second (advance) side surface 16 e (shown in FIG. 2) of the widest vane 16 a abuts against a projecting surface 10 c formed in a confront side surface of the adjacent partition wall 10 on the advance side (or clockwise side), and this abutment determines the rotational angular relative position of vane member 9 of the greatest advance angle.

In these states shown in FIG. 3 and FIG. 4, the other vanes 16 b and 16 c are in a non-abutting free state without abutting against either of the confronting side surfaces of the adjacent partition walls 10 on the retard and advance side. This arrangement is helpful for improving the abutment accuracy between the vane member 9 and the partition walls 10, and improving the responsiveness or response speed of vane member 9 in rotating in the forward direction and reverse direction by increasing the supply speed of the oil pressure to the pressure chamber 11 or 12 as mentioned later.

Each of the (three) retard fluid pressure chambers 11 is defined between the second (advance) side surface of one of the vanes 10 facing in the second (advance) rotational (clockwise) direction and the first (retard) side surface of the adjacent partition wall facing in the first (retard) rotational (counterclockwise) direction on the advance (clockwise) side. Similarly, each of the (three) advance fluid pressure chambers 12 is defined between the first (retard) side surface of one of the vanes 10 facing in the first (retard) rotational (counterclockwise) direction and the second (advance) side surface of the adjacent partition wall facing in the second (advance) rotational (clockwise) direction on the retard (counterclockwise) side. Each of the retard pressure chambers 11 is connected through a radially extending communicating hole 11 a formed in the central rotor 15, with the first hydraulic circuit 4. Similarly, each of the advance pressure chambers 12 is connected through a radially extending communicating hole 12 a formed in the central rotor 15, with the first hydraulic circuit 4.

First hydraulic circuit 4 is configured to control the supply and drain of the operating oil (fluid pressure) for the retard and advance chambers 11 and 12 selectively. As shown in FIG. 1, the first hydraulic circuit 4 includes a retard pressure passage 18, an advance pressure passage 19, an fluid pump or oil pump 20, and a first electromagnetic selector valve 21. The retard pressure passage 18 is a passage for supplying and draining the operating fluid to and from each retard chamber 11 through one of the first communication holes 11 a. The advance pressure passage 19 is a passage for supplying and draining the operating fluid to and from each advance chamber 12 through one of the second communication holes 12 a. The fluid pump 20 is a fluid pressure source for selectively supplying the fluid pressure to the retard or advance pressure passages 18 or 19. Fluid pump 20 of this example is an oil pump of a known type, such as a trochoid pump, driven by the crankshaft of the engine.

Retard pressure passage 18 extends from a first port or retard pressure port of first electromagnetic selector valve 21 to an axial passage 18 a extending axially in a passage forming end member 37 having an approximately cylindrical shape inserted and held in the central rotor 15 of vane rotor 9 and the seal guide portion 15 a. Retard fluid passage 18 is connected through the axial passage 18 a and the first communication passages 11 a to the retard pressure chambers 11. Similarly, the advance fluid passage 19 extends from a second port or advance pressure port of first electromagnetic selector valve 21 to an axial passage 19 a extending axially in the passage forming end member 37. Advance fluid passage 19 is connected through the axial passage 19 a and the second communication passages 12 a to the advance pressure chambers 12.

The passage forming end member 37 includes an external end portion fixed to a chain cover (not shown) so that the external end portion is non-rotational, and an internal axial portion formed with the passage 18 a and 19 a and a passage 34 a of a second hydraulic circuit 28 for unlocking a lock mechanism as mentioned later.

As shown in FIG. 1, first electromagnetic selector valve 21 of this example is a 4-port, 3-position proportional type valve configured to move a spool (not shown) axially back and forth in a bore of a valve body under the control of an electronic controller (not shown) to select one of three valve positions. In a first valve position, the selector valve 21 connects the retard pressure passage 18 with a discharge or outlet passage 20 a of oil pump 20, and connects the advance pressure passage 19 with a drain passage 22 leading to an oil pan 23. In a second valve position, the selector valve 21 connects the retard pressure passage 18 with the drain passage 22, and connects the advance pressure passage 19 with the discharge passage 20 a of oil pump 20. At the time of stoppage of the engine or in some other situation, the selector valve 21 is held at a third (intermediate) position to seal off the operating fluid in the pressure chambers 11 and 12, by shutting the retard and advance passages 18 and 19 off from the discharge passage 20 a and drain passage 22.

A suction or inlet passage 20 b of oil pump 20 and the drain passage 22 are connected to the inside of oil pan 23. A main oil gallery M/G for supplying a lubricating oil to sliding contact portions in the internal combustion engine is connected to a junction point on the downstream side of discharge passage 20 a of oil pump 20. A filter 50 is provided on the downstream side of discharge passage 20 a of oil pump 20. Oil pump 20 is provided with a flow control valve 51 for controlling the discharge fluid quantity to a desired level by returning an excess amount of the discharged operating oil from the discharge passage 20 a to oil pan 23.

The electronic controller includes a computer configured to sense one or more current engine operating conditions by receiving input information from various sensors such as a crank angle sensor (for sensing an engine speed), an airflow meter, an engine coolant temperature sensor, an engine temperature sensor, a throttle valve opening sensor, and a cam angle sensor for sensing a current rotational phase of camshaft 2, and to control the position of the spool in each of the first electromagnetic selector valve 21 and a later-mentioned second electromagnetic selector valve 36 by delivering a control pulse current to the electromagnetic coil of that selector valve in accordance with the sensed engine operating conditions.

In this embodiment, there is provided a holding device (or position holding means) to hold the vane member 9 relative to housing 7 at an intermediate rotational phase position (shown in FIG. 2) intermediate between the most retard rotational position (shown in FIG. 3) and the most advance rotational position (shown in FIG. 4).

As shown in FIGS. 5˜10, the holding device serving as a lock mechanism includes first and second lock hole forming members 1 a and 1 b formed, respectively, with first and second lock holes 24 and 25, first and second lock pins 26 and 27 for engaging with the lock holes 24 and 25, respectively, and the before-mentioned second hydraulic circuit 28 (shown in FIG. 1). The lock hole forming members 1 a and 1 b are provided in the inner side surface (1 c) of sprocket 1 at predetermined circumferential positions. Each of lock hole forming members 1 a and 1 b has a T-shaped section. Each of the lock holes 24 and 25 serves as a lock portion or lock receiving portion whereas each of the lock pins 26 and 27 serves as a lock member. The first and second lock pins 26 and 27 are provided, respectively, in the vane 16 a and vane 16 b and arranged to engage with the first and second lock holes 24 and 25, respectively. The second hydraulic circuit 28 is arranged to cancel the engagement of first and second lock pins 26 and 27 with respect to the first and second lock holes 24 and 25. Second hydraulic circuit 28 serves as at least part of a canceling section or means.

The first lock hole 24 is elongated in the circumferential direction of sprocket 1 in the form of a circular arc (like a cocoon), as shown in FIGS. 2˜4. First lock hole 24 is formed in the inner side surface 1 c of sprocket 1, at an intermediate position shifted from the most retard position of vane member 9 toward the advance side. Moreover, first lock hole 24 has a stepped bottom depressed stepwise from the retard side to the advance side, so as to form a plurality of steps (three steps in this example) serving as a first lock guide groove.

As shown in FIGS. 5˜10, the first lock guide groove includes a first bottom surface 24 a depressed from the inner side surface 1 c of sprocket 1 as an uppermost surface, a second bottom surface 24 b depressed from the first bottom surface 24 a, and a third bottom surface 24 c depressed from the second bottom surface 22 b. An inner side surface 24 d on the retard pressure chamber's side stands upright from the lowest bottom surface 24 c. A forward end portion 26 a of the first lock pin 26 descends stepwise from the inner side surface 1 c of sprocket 1, through the first and second bottom surfaces 24 a and 24 b to the lowest third bottom surface 24 c in the advance direction. On each of the bottom surfaces 24 a, 24 b and 24 c, the forward end portion 26 a of first lock pin 26 is prevented from moving in the retard direction by a riser wall surface on the retard side. Thus, the staircase of the stepwise bottom surfaces 24 a, 24 b and 24 c functions as a one-way clutch (ratchet).

The movement of first lock pin 26 in the advance direction (toward the adjacent retard pressure chamber 11) is limited by the abutment of the forward end portion 26 a against the inner side surface 24 d (as shown in FIG. 10).

As shown in FIGS. 2˜5, the second lock hole 25 is elongated in the circumferential direction of sprocket 1 in the form of a circular arc like the first lock hole 24. Second lock hole 25 is formed in the inner side surface 1 c of sprocket 1, at an intermediate position shifted from the most retard position of vane member 9 toward the advance side. Moreover, second lock hole 25 has a stepped bottom depressed stepwise from the advance chamber's side to the retard chamber's side, so as to form a plurality of steps (two steps in this example) serving as a second lock guide groove.

As shown in FIGS. 5˜10, the second lock guide groove includes a first bottom surface 25 a depressed from the inner side surface 1 c of sprocket 1 as an uppermost surface, and a second bottom surface 25 b depressed from the first bottom surface 25 a. An inner side surface 25 c on the retard pressure chamber's side stands upright from the lowest bottom surface 25 b. The depth of first bottom surface 25 a is made, through a riser wall surface rising from the first bottom surface 25 a, slightly greater than the depth of the first bottom surface 24 a of the first lock hole 24. The depth of the second bottom surface 25 b is set, through the riser wall surface 25 c, equal to a sum of the depth of the second bottom surface 24 b and the depth of the third bottom surface 24 c. Accordingly, the total depth of second lock hole 25 from the inner side surface 1 c of sprocket 1 to the deepest bottom 25 b is substantially equal to the total depth of first lock hole 24 from the inner side surface 1 c of sprocket 1 to the deepest bottom 24 c, and the deepest bottom surface 25 b of second lock hole 25 is substantially equal in depth to the deepest bottom surface 24 c of first lock hole 24. A forward end portion 27 a of the second lock pin 27 descends stepwise from the inner side surface 1 c of sprocket 1, through the first bottom surface 25 a to the lowest second bottom surface 25 b in the advance direction. On each of the bottom surfaces 25 a and 25 b, the forward end portion 27 a of second lock pin 27 is prevented from moving in the retard direction by a riser wall surface on the retard side. Thus, the staircase of the stepwise bottom surfaces 25 a and 25 b functions as a one-way clutch (ratchet).

The movement of second lock pin 27 in the retard direction (toward the advance pressure chamber 12) is limited by the abutment of the forward end portion 27 a against the riser wall surface 25 c of the second bottom surface 25 b (as shown in FIG. 10).

The positions of first and second lock holes 24 and 25 relative to each other are set as shown in FIGS. 5˜10. In the stages in which the first lock pin 26 abuts on the first, second or third bottom surface 24 a, 24 b or 24 c of first lock hole 24, the second lock pin 27 is held still in the state in which the forward end 27 a of second lock pin 27 abuts on the inner side surface 1 c of sprocket 1, as shown in FIGS. 5˜8.

Thereafter, as shown in FIGS. 9 and 10, the second lock pin 27 first enters the second lock hole 25 and the forward end portion 27 a of second lock pin 27 abuts on the first bottom surface 25 a of second lock hole 25 when the forward end portion 26 a of first lock pin 26 moves on the lowest third bottom surface 24 c slightly toward the advance side in first lock hole 24. When the first lock pin 26 slides on third bottom surface 24 c toward the advance side and abuts against the inner side surface 24 d, the forward end portion 27 a of second lock pin 27 abuts against the lowest second bottom surface 25 b and abuts again the riser wall surface 25 c. The first and second lock holes 24 and 25 are positioned relative to each other in this way.

Thus, as the vane rotor 9 rotates relatively from a predetermined retard side position to an advance side position, the first lock pin 26 first descends the stairway of bottom surfaces 24 a, 24 b and 24 c of first lock hole 24, and subsequently the second lock pin 27 descends the stairway of bottom surfaces 25 a and 25 b of second lock hole 25. Therefore, the vane rotor 9 rotates relatively in the advance direction with receiving limitation of a five-step ratchet function of limiting rotation in the retard direction, and finally reaches the intermediate phase position between the most retard phase angle and the most advance phase angle. Then, vane rotor 9 is held at the intermediate phase position.

First lock pin 26 is slidably received in a first pin hole 31 a opened axially through the first vane 16 a having the greatest circumferential width, as shown in FIG. 1 and FIG. 5. First lock pin 26 has a stepped outside circumference. The forward end portion 26 a is a portion having the smallest outside diameter. In addition to forward end portion 26 a, the first lock pin 26 has an intermediate portion 26 b having a medium outside diameter, extending from the forward end portion 26 a toward the rear end of first lock pin 26, and a first pressure receiving portion 26 c shaped like an outward flange forming a greatest diameter portion on the rear side of intermediate portion 26 b. In this example, the forward end portion 26 a, intermediate portion 26 b and first pressure receiving portion 26 c are integral parts of the single integral first lock pin 26.

The intermediate portion 26 b of first lock pin 26 is fit slidably and liquid-tightly in a sleeve 40 forcibly fit in a forward portion of the first pin hole 31 a. A rear end portion 26 d of first lock pin 26 on the rear side of first pressure receiving portion 26 c is slidable liquid-tightly in the first pin hole 31 a. The forward end portion 26 a has a flat end surface which can abut on each of the bottom surfaces 24 a˜24 c snugly and tightly.

A first spring 29 is arranged to urge the first lock pin 26 toward the first lock hole 24. First spring 29 is disposed in an inside bore or recess formed in first lock pin 26, between the bottom of the inside bore and the inside wall surface of front cover 13 confronting the first lock hole 24 across first lock pin 26. The first spring 29 serves as an urging member or biasing member.

First lock pin 26 is arranged to receive equal fluid pressures on a front portion and a rear portion. In this example, the forward end portion 26 a and rear end portion 26 d are arranged to receive the same fluid pressure from the advance pressure chambers 12, respectively, through front and rear fluid holes 45 a and 45 b formed in the vane 16 a. The fluid pressure from the front fluid hole 45 a is applied to a forward end surface 26 f of the forward end portion 26 a and an forward facing annular surface 26 g of the front end of intermediate portion 26 b. On the other hand, the pressure from the rear fluid hole 45 b is applied to a rear end surface 26 h of the rear end portion 26 d, and the bottom surface 26 i of spring groove. The pressure receiving area on the front side equaling the sum of the area of the forward end surface 26 f of the forward end portion 26 a and the area of the forward facing annular surface 26 g is equal to the pressure receiving area on the rear side equaling the sum of the area of the rear end surface 26 h of the rear end portion 26 d, and the area of the bottom surface 26 i of spring groove. The equal pressure of the advance pressure chambers 12 is applied simultaneously to the equal pressure receiving areas on the front side and the rear side in the opposite directions (the forward direction toward the lock hole and the rearward direction away from the lock hole).

Moreover, the first pressure receiving portion 26 c includes a forward facing first pressure receiving (annular shoulder) surface 26 e for receiving the fluid pressure of a first cancel pressure chamber 32 as mentioned later. On the other hand, the first pressure receiving portion 26 c includes a rearward facing atmospheric pressure receiving (annular shoulder) surface opening to the atmosphere through a hole 43 (air passage) formed in vane 16 a and front cover 13.

Second lock pin 27 is slidably received in a second pin hole 31 b opened axially through the second vane 16 b having the medium circumferential width. Second lock pin 27 has a stepped outside circumference like the first lock pin 26. The forward end portion 27 a is a portion having the smallest outside diameter. In addition to forward end portion 27 a, the second lock pin 27 has an intermediate portion 27 b having a medium outside diameter, extending from the forward end portion 27 a toward the rear end of second lock pin 27, and a second pressure receiving portion 27 c shaped like an outward flange forming a greatest diameter portion on the rear side of intermediate portion 27 b. In this example, the forward end portion 27 a, intermediate portion 27 b and second pressure receiving portion 27 c are integral parts of the single integral second lock pin 27.

The intermediate portion 27 b of second lock pin 27 is fit slidably and liquid-tightly in a sleeve 41 forcibly fit in a front potion of the second pin hole 31 b. A rear end portion 27 d of second lock pin 27 on the rear side of second pressure receiving portion 27 c is slidable liquid-tightly in the second pin hole 31 b. The forward end portion 27 a has a flat end surface which can abut on each of the bottom surfaces 25 a and 25 b snugly and tightly.

A second spring 30 is arranged to urge the second lock pin 27 toward the second lock hole 25. Second spring 30 is disposed in an inside bore or recess formed in second lock pin 27, between the bottom of the inside bore and the inside wall surface of front cover 13 confronting the second lock hole 25 across second lock pin 27. Second spring 30 serves as the urging member or biasing member.

Second lock pin 27 is arranged to receive equal fluid pressures on a front portion and a rear portion. In this example, the forward end portion 27 a and rear end portion 27 d are arranged to receive the same fluid pressure from the advance pressure chambers 12, respectively, through front and rear fluid holes 46 a and 46 b formed in the vane 16 b. The fluid pressure from the front fluid hole 46 a is applied to a forward end surface 27 f of the forward end portion 27 a and an forward facing annular surface 27 g of the front end of intermediate portion 27 b. On the other hand, the pressure from the rear fluid hole 46 b is applied to a rear end surface 27 h of the rear end portion 27 d, and the bottom surface 27 i of spring groove. The pressure receiving area on the front side equaling the sum of the area of the forward end surface 27 f of the forward end portion 27 a and the area of the forward facing annular surface 27 g is equal to the pressure receiving area on the rear side equaling the sum of the area of the rear end surface 27 h of the rear end portion 27 d, and the area of the bottom surface 27 i of spring groove. The equal pressure of the advance pressure chambers 12 is applied simultaneously to the equal pressure receiving areas on the front side and the rear side.

Moreover, the second pressure receiving portion 27 c includes a forward facing second pressure receiving (annular) surface 27 e for receiving the fluid pressure of a second cancel pressure chamber 33 as mentioned later. On the other hand, the second pressure receiving portion 27 c includes a rearward facing atmospheric pressure receiving (annular) surface opening to the atmosphere through a hole 44 (air passage) formed in vane 16 b and front cover 13.

As shown in FIGS. 1 and 5, the second hydraulic circuit 28 includes a supply/drain passage 34 for supplying the fluid pressure to the first cancel pressure chamber 32 formed between the larger diameter portion of first pin hole 31 a and the first pressure receiving portion 26 c of first lock pin 26, and the second cancel pressure chamber 33 formed between the larger diameter portion of second pin hole 31 b and the second pressure receiving portion 27 b of second lock pin 27, through a supply branch passage 35 a branching from the discharge passage 20 a of the oil pump 20, and for draining the operating fluid from the first cancel pressure chamber 32 and the second cancel pressure chamber 33 through a drain branch passage 35 b branching from the drain passage 22. Hydraulic circuit further includes the before-mentioned second electromagnetic selector valve 36 for connecting the supply/drain passage 34 selectively with the supply branch passage 35 a and the drain branch passage 35 b in accordance with the engine operating condition(s).

The first cancel pressure chamber 32 receives the fluid pressure, applies the received pressure to the first pressure receiving surface 26 e, and thereby withdraws the first lock pin 26 from the first lock hole 24 against the spring force of the first spring 29 to disengage the first lock pin 26 from first lock hole 24. Similarly, the second cancel pressure chamber 33 receives the fluid pressure, applies the received pressure to the second pressure receiving surface 27 e, and thereby withdraws the second lock pin 27 from the second lock hole 25 against the spring force of the second spring 30 to disengage the second lock pin 27 from second lock hole 25.

The supply/drain passage 34 extends from a first end connected with a port of second electromagnetic valve 36, to a second end connected with supply/drain branch passages 34 a formed in the passage forming member 37. Each of supply/drain branch passages 34 a first extends axially, and is bent to a radial direction. The supply/drain branch passages 34 a are connected, respectively, through the first and second fluid passage holes 38 a and 38 b, with the first and second cancel pressure chambers 32 and 33.

The passage forming member 37 includes annular grooves formed in the outside circumference surface at axial positions and arranged to receive (three) annular seal members 39, respectively, to sealingly separate the open ends of the passages 18 a and 19 a and the supply/drain passages 34 a opened in the support hole 15 d.

The second electromagnetic selector valve 36 of this example is a 4-port, 3-position proportional type valve configured to move a spool (not shown) axially back and forth against a valve spring by an on-off control current delivered from the electronic controller. Thus, second electromagnetic valve 36 connects the supply/drain passage 34, selectively with the passage 35 a or 35 b, and seals off the operating fluid in the cancel pressure chambers 32 and 33, by shutting the supply/drain passage 34 off from the passages 35 a and 35 b.

[OPERATIONS] The thus-constructed valve timing control apparatus or system is operated as follows:

[OPERATION CONTROL AFTER SHORT STOP] When the engine is stopped by turn-off of the ignition switch after a normal vehicle driving operation, the oil pump 20 is stopped too. Accordingly, the supply of the operating oil to the pressure chambers 11 or 12 is stopped, and the vane rotor 9 is allowed to rotate freely in the forward and backward directions. When the cam torque timing in the alternating torque at the time of the engine stoppage is a negative torque, the vane rotor 9 rotates in the advance direction and the system becomes unable to hold the vane rotor 9 at the most retard phase, so that an engine stop control is required to achieve a positive torque at the time of engine stoppage.

In this case, the electronic controller supplies electricity to first electromagnetic selector valve 21, thereby holds the spool at the intermediate neutral position, and shuts the passages 18 and 19 from the passages 20 a and 22.

In the stop state in which the drive of oil pump 20 is stopped, the operating fluid in discharge passage 20 a may return from oil pump 20 to oil pan 23 because of the lift (or head) of the pump, and moreover the operating fluid in the pressure chambers 11 and 12 may flow downwards. If the operating oil is removed from pressure chambers 11 and 12, the vane rotor 9 at the most retard side may flap due to the alternating torque at the time of an engine start, and cause flapping noises by collision with the partition walls 10. Therefore, the control system according to this embodiment seals the operating fluid in the pressure chambers 11 and 12 by shutting off the fluid passages 18 and 19, and thereby prevent flapping of vane rotor 9.

If the engine is restarted in the state in which the warm up state is maintained, after the elapse of a short time within 15 minutes, for example, the effective compression ratio is lowered because, at this instant, the vane rotor 9 is held at the rotational phase position on the most retard side shown in FIG. 3, and the closing timing of the intake valve is on the retard side of the piston bottom dead center. Accordingly, the system can reduce the pumping loss, restrain undesired vibrations and improve the engine starting performance.

The above-mention operation control after a short time stoppage is performed, for example, in the case of idling stop of stopping the operation of the engine during a driving operation of the vehicle automatically irrespectively of turn on/off of the ignition switch when the time from a stop to a restart is short. The system can lower the effective compression ratio and improve the engine starting performance in the same manner.

[OPERATION CONTROL AFTER LONG STOP] When the ignition key is turned to start cranking after the elapse of a long time longer than 15 minutes, for example, in the state in which the engine is cooled, then the electronic controller shifts the spool in first electromagnetic selector valve 21 axially to the valve position to connect the discharge passage 20 a with one of the retard pressure passage 18 and advance pressure passage 19, and to connect the drain passage 22 with the other of the retard and advance pressure passages 18 and 19.

Simultaneously, the electronic controller energizes the second electromagnetic selector valve 36 to connect the supply/drain passage 34 with the drain branch passage 35 b. Therefore, the operating fluid is drained from the first and second cancel pressure chambers 32 and 33, and the first and second lock pins 26 and 27 are urged forwards (toward the respective lock holes 24 and 25) by the springs 29 and 30, respectively.

In this early stage of the cranking operation, the discharge pressure of oil pump 20 is still low, the oil pressure supplied through the one of the retard and advance pressure passage 18 and 19 is still low.

Therefore, the vane rotor or vane member 9 rotates slightly to the advance side by the alternating torque acting on camshaft 2, specifically by the negative torque, and hence the forward end portion 26 a of first lock pin 26 abuts on the first bottom surface 24 a of first lock hole 24, as shown in FIGS. 5 and 6. In this state, the positive toque acts on the lock pin 26 to try rotating the lock pin 26 in the retard side. However, the forward end portion 26 a abuts against the riser wall surface rising from the first bottom surface 24 a, and this abutment prevents the rotation toward the retard side.

Thereafter, the first lock pin 26 descends stepwise through second bottom surface 24 b to third bottom surface 24 c and slides on the third bottom surface 24 c to the advance side as shown in FIGS. 7˜9 in accordance with rotation of vane rotor 9 to the advance side due to the negative torque, while the first lock pin 26 is receiving the ratchet function. Moreover, as shown in FIGS. 9 and 10, the forward end portion 27 a of second lock pin 27 descends stepwise through first bottom surface 25 a to second bottom surface 25 b of second lock hole 25 while receiving the ratchet function, and finally the second lock pin 27 is held at the position on second bottom surface 25 b.

In this state, as shown in FIG. 10, the first lock pin 26 is held at the position by the abutment of the forward end portion 26 a against the inner side wall surface 24 d rising from third bottom surface 24 c on the advance side (on the retard chamber's side), and the second lock pin 27 is held at the position by the abutment of forward end portion 27 a against the inner side wall surface 25 c rising from second bottom surface 25 b on the advance chamber's side. Therefore, the first and second lock pins 26 and 27 are held at the respective positions stably.

With this operation of the lock pins 26 and 27, the vane rotor 9 is held at the intermediate phase position as shown in FIG. 2, and the system controls the intake valve closing timing at a position on the advance side before the piston bottom dead center. Therefore, the system can improve the combustion by increasing the engine compression ratio, and improve the startability in a cold state.

When the normal engine operation is started after the warm-up of the engine, and the engine speed enters a high speed range, for example, then the first electromagnetic selector valve 21 connects the discharge passage 20 a with advance pressure passage 19 and connects the drain passage 22 with retard pressure passage 18.

Therefore, the pressure in each retard pressure chamber 11 becomes lower and the pressure in each advance pressure chamber 12 becomes higher. As a result, the vane rotor 9 is rotated to the most advance side. Thus, the system can advance the intake valve opening timing, increase the overlap with the exhaust valve, and increases the engine output by increasing the intake air quantity.

In this state, as mentioned before, the second electromagnetic selector valve 36 is held in the position to supply the fluid pressure to each of the pressure chambers 32 and 33 by connecting the supply/drain passage 34 with supply passage 35 a and to shut off the drain passage 35 b. Therefore, the vane rotor 9 is allowed to rotate freely.

In this way, the control system according to this embodiment is arranged to vary the engine compression ratio at the time of a restart, in accordance with the time length of the engine stop period, that is, the temperature of the engine. Therefore, the system can improve the engine startability by reducing the torque load at the time of a start, reduce vibrations and improve the exhaust emission performance.

Furthermore, the position holding device or means (26, 27, 24, 25, 28) can hold the vane rotor 9 reliably at the intermediate phase position. The lock guide groove of each lock hole (24, 25) is arranged to have the stepped bottom (24 a˜24 c, 25 a˜25 b) to guide the lock pin only in the direction toward the lock hole (24, 25), so that the lock pin is guided reliably and stably.

The operating fluid pressure for the cancel pressure chambers 32 and 33 is prepared by a hydraulic circuit separately from the pressure for the retard and advance chambers 11 and 12. Therefore, the system can supply the operating fluid pressure responsively to the cancel chambers 32 and 33, as compared to the arrangement using the fluid pressure for the chambers 11 and 12 to the chambers 32 and 33. As a result, the system can move each lock pin 26 or 27 rearwards quickly, and eliminate the need for seal mechanism between the chambers 11 and 12 and the chambers 32 and 33.

Instead of providing air passages to both axial ends of a lock pin as in the earlier technology, each lock pin (26, 27) according to the embodiment is balanced in the axial direction by the application of the oil pressure on both ends of the lock pin to ensure smooth movement of the lock pin. Therefore, the system can move the lock pin quickly in the axial direction by the spring (29, 30) and the cancel pressure in the cancel pressure chamber (32, 33).

Thus, the system according to the embodiment can achieve the same effect of air passages by applying the equal oil pressures to the forward end portion and riverward end portion of the lock member without the need for forming an air passage in the lock hole forming member (1 a, 1 b). Therefore, it is possible to reduce side clearances between both axial end surfaces of the widest vane 16 a and the confronting surfaces of front cover 13 and sprocket 1.

Therefore, it is possible to reduce the circumferential width of the widest vane 16 a as compared to the earlier technology. Consequently, it is possible to increase the rotational angular range of vane rotor 9 relative to housing 7 by increasing the angular range of vane 16 a between the circumferentially confronting side surfaces 10 b and 10 c of the partition walls 10.

The air holes 43 and 44 for leading the upper side surfaces of first and second pressure receiving portions 26 c and 27 c opposite to the pressure receiving surfaces 26 e and 27 e, to the outside or the atmosphere are formed in the vanes 16 a and 16 b and the front cover 13. There are no connections with the advance pressure chambers 12, so that the operating fluid does not leak in this portion.

The arrangement of supplying the advance pressure of advance chambers 12 to both of the forward and rearward end portions of the lock pin (26, 27) is effective for stabilizing the behavior of the lock pin. At the time of engine start, air may be involved in the operating oil supplied to retard chambers 11. Therefore, if this operating oil is supplied to both ends of each lock pin 26 or 27, the air involved in the operating oil might make unstable the behavior of the lock pin, resulting in generation of undesired noises. On the other hand, the operating oil supplied to advance chambers 12 during steady state operation after engine start is almost free from air involvement. Therefore, the arrangement of supplying the advance pressure of advance chambers 12 to both ends of the lock pin can make stable the behavior of the lock pin (26, 27) and prevent generation of undesired noises.

The riser wall surface 25 c between first and second bottom surfaces 25 a and 25 b of the second lock guide groove is made high. This riser wall structure can increase the strength, and improve the durability of enduring repetitive collision of the second lock pin 27 against the riser wall surface 25 c. When, on the other hand, first lock pin 26 is engaged with first lock hole 24, the forward end portion 26 a abuts against the inner side surface 24 d rising from the deepest bottom surface 24 c and having a greater surface area. This structure further improves the durability.

Each of the first and second lock guide grooves is cocoon-shaped. Therefore, each of first and second lock pins 26 and 27 can move smoothly in the guide groove with rotation of vane rotor 9.

The illustrated example of the embodiment employs, as a parameter, the elapsed time from an engine stop to a restart. By using the engine temperature sensed by the engine temperature sensor directly as the parameter, instead of using the elapsed time, it is possible to a practical control system arranged to control the valve timing in accordance with the engine temperature, for example by examining whether the engine temperature is lower than or equal to a predetermined temperature or higher than the predetermined temperature.

In the illustrated example, the position holding device is constructed by the first lock section including first lock pin 26 and first, second and third bottom surfaces 24 a˜24 c and the second lock section including second lock pin 27 and first and second bottom surfaces 25 a and 25 b. Therefore, it is possible to reduce the wall thickness of the sprocket 1 in which the lock holes 24 and 25 are formed. The arrangement using a single lock pin and a single staircase of steps 24 a, 24 b, 24 c, 25 a and 25 b requires a thick wall for the sprocket 1 to ensure the height of this staircase. By contrast, the arrangement of the illustrated example makes it possible to reduce the wall thickness of sprocket 1, to reduce the axial dimension of the valve timing control apparatus and to improve the flexibility of the layout.

The lock member (26, 27) is in the form of a cylindrical lock pin and the pressure receiving portion (26 c, 27 c) is in the form of an outward flange. Therefore, the lock member can be fabricated easily and inexpensively.

The present invention is not limited to the illustrated embodiment. The valve timing control apparatus according to the present invention can be applied not only to the intake side, but also to the exhaust side.

According to one of possible interpretations of the illustrated embodiment, a valve timing control apparatus includes a basic structure which comprises: a driving rotary member adapted to receive a rotational force from a crankshaft; a vane rotor which is adapted to be connected with a camshaft, which is arranged to rotate relative to the driving rotary member, and which includes at least one vane defining a retard pressure chamber and an advance pressure chamber in the inside (cavity) of the driving rotary member; a lock member received in the vane and arranged to slide axially; a lock receiving portion such as a lock hole (formed in the driving rotary member (lock hole forming member 1 a, 1 b)) to receive a forward end of the lock member when the vane is rotated relatively to a predetermined angular position; and a biasing member to urge the lock member toward the lock receiving portion. The lock member includes forward and rearward end portions arranged to receive equal fluid pressures, respectively, in rearward and forward directions (to balance the lock member in an axial direction). In addition to the basic structure, the valve timing control apparatus may further comprise any one or more of following features (f1)˜(f19).

(f1)) The lock member (26, 27) may further include a pressure receiving portion (26 c, 27 c) (in the form of an outward flange, in the illustrated example) including a first surface (26 e, 27 e) (lower surface) to which an operating fluid pressure (cancel pressure) is selectively applied, and a second surface (upper surface) which is opened, through an air passage (43, 44) formed in the vane rotor, to the atmosphere (to an outside to receive an atmospheric pressure). (f2) The valve timing control apparatus further comprises a canceling section to release the lock member from the lock receiving portion (lock hole) selectively.

(f3) The lock hole is elongated circumferentially so as to form a lock guide groove elongated in one of an advance direction and a retard direction (or circumferentially around the center axis of the vane rotor 9) and arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the lock member is received in the lock guide groove. (f4) The lock member is a lock pin including a (cylindrical) shank and an (circular) outward flange (26 c, 27 c) serving as the pressure receiving portion (formed between the forward end portion (26 a, 27 a) and the rearward end portion (26 d, 27 d)). In this case, the lock member can make easier the production process and prevent an increase of the manufacturing cost.

(f5) The driving rotary member includes a cylindrical housing including at least one shoe or partition wall projecting radially inwards, and a cover member closing an open end of the housing and including a through hole formed on a radial inner side of an outside circumference of the vane rotor, the vane is formed with the air passage extending to the though hole of the cover member and thereby opening the second surface of the pressure receiving portion to the atmosphere. (f6) The valve timing control apparatus further comprises a first hydraulic circuit (4, 21) to regulate the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber, and a second hydraulic circuit (28, 36) to supply the operating fluid pressure different from the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber. This feature can improve the response speed for supplying the operating fluid pressure to the cancel pressure chamber for the pressure receiving portion, and eliminate the need for seals in various portions.

(f7) The first hydraulic circuit includes a first control valve to regulate the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber, and the second hydraulic circuit includes a second control valve to regulate the operating fluid pressure applied to the first surface of the pressure receiving portion of the lock member. (f8) The second control valve is a selector valve having at least a first valve position to increase the operating fluid pressure (by connecting a cancel pressure chamber (32, 33) with a pump outlet passage 20 a) and a second valve position to decrease the operating fluid pressure (by connecting the cancel pressure chamber (32, 33) with a drain passage 22).

(f9) The first fluid pressure received by the forward end portion (26 a, 27 a) and the rearward end portion (26 b. 27 b) of the lock member (26, 27) is the fluid pressure in the advance pressure chamber. In this case, the advance fluid pressure is applied equally to both of the forward end portion and the rearward end portion, so that the forward force and rearward force produced by the fluid pressures are balanced and the lock member can move quickly by the operating fluid pressure applied to the pressure receiving portion (and a biasing member). (f10) The lock guide groove includes a stepped bottom descending stepwise toward the lock hole (or toward the deepest bottom).

(f11) In addition to the vane which is a first vane, the lock member which is a first lock member received in the first vane, the lock hole which is a first lock hole, the biasing member which is a first biasing member, the vane rotor further includes a second vane defining a retard pressure chamber and an advance pressure chamber in the inside of the driving rotary member, and the valve timing control apparatus further comprises a second lock member received in the second vane and arranged to slide forwards and rearwards in the axial direction (of the vane rotor 9), a second lock hole (formed in the driving rotary member (lock hole forming member 1 a, 1 b)) to receive a forward end of the second lock member when the second vane is at a predetermined angular position, and a second biasing member to urge the second lock member toward the second lock hole. The second lock member includes forward and rearward end portions arranged to receive equal fluid pressures, respectively, in rearward and forward directions (to balance the lock member in the axial direction). The second lock member (26, 27) may further include a pressure receiving portion (26 c, 27 c) (outward flange) including a first surface (26 e, 27 e) (lower surface) to which an operating fluid pressure (cancel pressure) is selectively applied, and a second surface (upper surface) which is opened, through an air passage (43, 44) formed in the vane rotor, to the atmosphere (to an outside to receive an atmospheric pressure).

(f12) Each of the first and second lock holes is elongated circumferentially so as to form a (first or second) lock guide groove elongated in one of an advance direction and a retard direction (or circumferentially around the center axis of the vane rotor 9) and arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the (first or second) lock member is received in the (first or second) lock guide groove. (f13) The first lock hole is arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the first lock member is received in the first lock guide groove, and the second lock hole is arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the second lock member is received in the second lock guide groove.

(f14) The first lock member and the first lock hole are arranged to allow rotation of the vane rotor relative to the driving rotary member within a predetermined angular range in a state in which the first lock member is engaged with the first lock hole; and the second lock member and the second lock hole are arranged to lock the vane rotor to prevent rotation of the vane rotor relative to the driving rotary member when the second lock member is engaged with the second lock hole (or the second lock member abuts on a lowest bottom (25 b) of the second lock hole) in the state in which the first lock member is engaged with the first lock hole. (f15) The second lock guide groove (or the second lock hole) includes a stepped bottom descending stepwise toward a deepest bottom. (f16) The first lock guide groove (or the first lock hole) includes a stepped bottom descending stepwise to a deepest bottom, and the first and second lock holes are so arranged that the second lock member descends the stepped bottom of the second lock guide groove and engages with the deepest bottom of the second lock hole after the first lock member descends the stepped bottom of the first lock guide groove and engages with the deepest bottom of the first lock hole. (f17) The number of steps of the stepped bottom of the first lock guide groove is greater than the number of steps of the stepped bottom of the second lock guide groove. (f18) The height of a riser wall surface rising from a lowest bottom surface (25 b) of the second guide groove is greater than the height of a riser wall surface rising from a lowest bottom surface (24 c) of the first lock guide groove. (f19) At least one of the first lock hole, the first lock guide groove, the second lock hole and the second lock guide groove is elongated circumferentially, or shaped like a cocoon.

This application is based on a prior Japanese Patent Application No. 2010-243845 filed on Oct. 29, 2010. The entire contents of this Japanese Patent Application are hereby incorporated by reference.

Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings. The scope of the invention is defined with reference to the following claims. 

1. A valve timing control apparatus comprising: a driving rotary member adapted to receive a rotational force from a crankshaft of an internal combustion engine; a vane rotor which is adapted to be fixed to a camshaft, which is arranged to rotate relative to the driving rotary member within a predetermined angular range, and which includes a vane defining a retard pressure chamber and an advance pressure chamber in an inside of the driving rotary member; a lock member received in the vane and arranged to slide forwards and rearwards in an axial direction; a lock hole to receive a forward end of the lock member when the vane is rotated relatively to a predetermined intermediate position between a most retard position and a most advance position; and a biasing member to urge the lock member toward the lock hole; wherein the lock member includes a forward end portion to receive a first fluid pressure which is one of a fluid pressure in the retard pressure chamber and a fluid pressure in the advance pressure chamber, in a pressure receiving area, and a rearward end portion to receive the first fluid pressure in a pressure receiving area, the forward and rearward end portions being so shaped that the pressure receiving area of the forward end portion receiving the first fluid pressure is equal to the pressure receiving area of the rearward end portion receiving the first pressure; and wherein the lock member further includes a pressure receiving portion including a first surface to which an operating fluid pressure is selectively applied, and a second surface which is opened through an air passage formed in the vane rotor, to atmosphere.
 2. The valve timing control apparatus as claimed in claim 1, wherein the lock hole is provided with a lock guide groove elongated circumferentially from the lock hole and arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the lock member is received in the lock guide groove.
 3. The valve timing control apparatus as claimed in claim 1, wherein the apparatus further comprises a canceling section to move the lock member out of the lock hole selectively.
 4. The valve timing control apparatus as claimed in claim 1, wherein the lock member is a lock pin including an outward flange serving as the pressure receiving portion.
 5. The valve timing control apparatus as claimed in claim 1, wherein the driving rotary member includes a cylindrical housing including a shoe projecting radially inwards, and a cover member closing an open end of the housing and including a through hole formed on a radial inner side of an outside circumference of the vane, the vane is formed with the air passage extending to the though hole of the cover member and thereby opening the second surface of the pressure receiving portion to the atmosphere.
 6. The valve timing control apparatus as claimed in claim 1, wherein the valve timing control apparatus further comprises a first hydraulic circuit to regulate the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber, and a second hydraulic circuit to supply the operating fluid pressure different from the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber.
 7. The valve timing control apparatus as claimed in claim 6, wherein the first hydraulic circuit includes a first control valve to regulate the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber, and the second hydraulic circuit includes a second control valve to regulate the operating fluid pressure applied to the first surface of the pressure receiving portion of the lock member.
 8. The valve timing control apparatus as claimed in claim 7, wherein the first control valve is a proportional control valve, and the second control valve has a first valve position to increase the operating fluid pressure and a second valve position to decrease the operating fluid pressure.
 9. The valve timing control apparatus as claimed in claim 1, wherein the first fluid pressure received by the forward end portion and the rearward end portion of the lock member is the fluid pressure in the advance pressure chamber.
 10. The valve timing control apparatus as claimed in claim 2, wherein the lock guide groove includes a stepped bottom descending stepwise toward the lock hole.
 11. The valve timing control apparatus as claimed in claim 1, wherein the vane is a first vane, the lock member is a first lock member received in the first vane, the lock hole is a first lock hole, the biasing member is a first biasing member, the vane rotor further includes a second vane defining a retard pressure chamber and an advance pressure chamber in the inside of the driving rotary member; the valve timing control apparatus further comprises a second lock member received in the second vane and arranged to slide forwards and rearwards in the axial direction, a second lock hole to receive a forward end of the second lock member when the second vane is at a predetermined intermediate position, and a second biasing member to urge the second lock member toward the second lock hole; wherein the second lock member includes a forward end portion to receive a second fluid pressure which is one of the fluid pressure in the retard pressure chamber and the fluid pressure in the advance pressure chamber in a pressure receiving area, and a rearward end portion to receive the second fluid pressure in a pressure receiving area, the forward and rearward portions being so shaped that the pressure receiving area of the forward end portion of the second lock member is equal to the pressure receiving area of the rearward end portion of the second lock member; and wherein the second lock member further includes a pressure receiving portion including a first surface to which an operating fluid pressure is selectively applied, and a second surface which is opened through an air passage formed in the vane rotor, to the atmosphere.
 12. The valve timing control apparatus as claimed in claim 11, wherein the first lock hole is provided with a first lock guide groove elongated in a circumferential direction around a rotation axis of the vane rotor from the first lock hole and arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the first lock member is received in the first lock guide groove, and the second lock hole is provided with a second lock guide groove elongated in the circumferential direction around the rotation axis of the vane rotor from the second lock hole and arranged to allow the vane rotor to rotate relative to the driving rotary member in a state in which the forward end of the second lock member is received in the second lock guide groove.
 13. The valve timing control apparatus as claimed in claim 12, wherein the first lock member and the first lock hole are arranged to allow rotation of the vane rotor relative to the driving rotary member within a predetermined angular range in a state in which the first lock member is engaged with the first lock hole; and the second lock member and the second lock hole are arranged to lock the vane rotor to prevent rotation of the vane rotor relative to the driving rotary member when the second lock member is engaged with the second lock hole in the state in which the first lock member is engaged with the first lock hole.
 14. The valve timing control apparatus as claimed in claim 13, wherein the second lock guide groove includes a stepped bottom descending stepwise toward the second lock hole.
 15. The valve timing control apparatus as claimed in claim 14, wherein the first lock guide groove includes a stepped bottom descending stepwise toward the first lock hole, and the first and second lock holes are so arranged that the second lock member descends the stepped bottom of the second lock guide groove and engages in the second lock hole after the first lock member descends the stepped bottom of the first lock guide groove and engages in the first lock hole.
 16. The valve timing control apparatus as claimed in claim 15, wherein a number of steps of the stepped bottom of the first lock guide groove is greater than a number of steps of the stepped bottom of the second lock guide groove.
 17. The valve timing control apparatus as claimed in claim 16, wherein a height of a riser wall surface rising from a lowest bottom surface of the second guide groove is greater than a height of a riser wall surface rising from a lowest bottom surface of the first lock guide groove.
 18. The valve timing control apparatus as claimed in claim 13, wherein at least one of the first lock hole, the first lock guide groove, the second lock hole and the second lock guide groove is elongated circumferentially.
 19. A valve timing control apparatus comprising: a driving rotary member adapted to receive a rotational force from a crankshaft; a vane rotor which is adapted to be fixed to a camshaft, which is arranged to rotate relative to the driving rotary member within a predetermined angular range, and which includes a vane defining a retard pressure chamber and an advance pressure chamber in an inside of the driving rotary member; a lock member received in the vane and arranged to slide axially; a lock receiving portion to receive a forward end of the lock member when the vane is rotated relatively to a predetermined intermediate position between a most retard position and a most advance position; and a biasing member to urge the lock member toward the lock receiving portion; wherein the lock member includes a forward end portion to receive a first fluid pressure which is one of a fluid pressure in the retard pressure chamber and a fluid pressure in the advance pressure chamber, and a rearward end portion to receive the first fluid pressure, the forward and rearward end portions being so shaped that a pressure receiving area of the forward end portion receiving the first fluid pressure is equal to a pressure receiving area of the rearward end portion receiving the first pressure; and wherein the valve timing control apparatus further comprises a canceling section to release the lock member from the lock receiving portion selectively.
 20. The valve timing control apparatus as claimed in claim 19, wherein the cancelling section includes a cancelling hydraulic circuit to supply a cancel fluid pressure to a cancel pressure chamber to apply the cancel pressure to a pressure receiving portion of the lock member to move the lock member against an urging force of the biasing member. 